Greetings:
When I deactivated Pretty Link Lite 1.7.2 (because I intended to update to 2.0.2 and have learned it’s usually better to deactivate a plugin before updating, because WP will refrain from reactivating it if it would cause a fatal error), I immediately got an Internal Server Error [how ironic! 
]. Only the admin is broken. The website is still functional and shows me as logged in.
I have tried checking the .htaccess and disabling all plugins, but neither allows me to access wp-admin.
How do I solve this? I need administrative access.